No, it’s not. It’s simply a choice you’re making. The only one forcing you to make it is you, not Blizzard and whatever sense of timing it might have.
And considering that there were plenty of groups I did the original Naxx with at level 70 - yes, I did not see the inside of the place until BC - that could not progress past maybe the first two bosses of the spider wing and maybe Patchwerk, even with T5 or T6 or equivalent gear, the fact that you think there will be any “drop in difficulty” in Naxx at all is amusing. The reason they rehashed it for Wrath is because so few people actually got to see it, much less clear it. (The Argent Dawn attunement grind is something else to keep in mind.)